1. Field of Invention
This invention relates to syringes for collecting blood samples, and more particularly syringes of the type that are used in drawing blood samples free of gaseous contaminates for use in blood gas analysis.
2. Description of the Prior Art
Syringe type devices are typically used for obtaining blood samples to perform blood gas analysis, which is an important diagnostic tool. Unfortunately, by the time a sample is withdrawn, treated with a liquid anticoagulant like heparin, and deposited for analysis, air and contaminates from the anticoagulant solution effect results when conventional syringes are used. One such blood collecting syringe is shown in U.S. Pat. No. 4,020,831 to Adler. Adler shows a holder and a plug which is so constructed that once the sample within the holder is placed in the centrifuge the plug seeks a level intermediate the densities between plasma and cell portions of the blood sample collected. No attempt is made to purge air from the sample.
Another syringe for collecting blood is shown in Johansen, U.S. Pat. No. 3,943,917 which discloses various types of structure for indenting a plunging sealing portion to allow communication between the interior chamber and the atmosphere so that a patient's blood pressure works to fill the interior chamber.
Currently the available syringes for obtaining a gas-free blood sample are disclosed in my pending U.S. Patent application for a SYRINGE DEVICE WITH MEANS FOR SELECTIVELY ISOLATING A BLOOD SAMPLE AFTER REMOVAL OF CONTAMINATES, Ser. No. 952,994, Filed Oct. 20, 1978, now U.S. Pat. No. 4,206,768, and U.S. Pat. Nos. 3,978,846 and 4,133,304, of which I am also the inventor. My pending application shows a plunger having a handle rotatable within and with respect to a dual circumferentially lipped sealing member. A thread or the like is extended across the sealing lips to interrupt the seal and is attached to the plunger handle. Once an individual's blood pressure fills the interior chamber of the syringe body, the seal interrupter can be wound onto the plunger handle to isolate a gas-free blood sample. Simultaneous treatment of the sample collected with an anticoagulant such as heparin is shown in my pending application, Ser. No. 50,970, filed June 22, 1979.